Field emission of electrons into vacuum from suitable cathode materials is useful for a variety of field emission devices including flat panel displays. Support pillars are important components of field emission devices (FEDs). A typical field emission device comprises a cathode including a plurality of field emitter tips and an anode spaced from the cathode. A voltage applied between the anode and cathode induces emission of electrons towards the anode. In flat panel displays an additional electrode called a gate is typically disposed between the anode and cathode to selectively activate desired pixels. The space between the cathode and anode is evacuated, and integrated cylindrical support pillars keep the cathode and anode separated. Without support pillars, the atmospheric pressure outside would force the anode and cathode surfaces together. Pillars are typically 100-1000 μm high and each provides support for an area of 1-10,000 pixels.
While cylindrical pillars may provide adequate mechanical support, they are not well suited for new field emission devices employing higher voltages. Applicants have determined that increasing the operating voltage between the emitting cathode and the anode can substantially increase the efficiency and operating life of a field emission device. For example, in a flat panel display, changing the operating voltage from 500 V to 5000 V could increase the operating life of a typical phosphor by a factor of 100. However, insulator breakdown and arcing along the surface of cylindrical pillars precludes the use of such high voltages.
If a cylindrical insulator is disposed between two electrodes and subjected to a continuous voltage gradient, then emitted electrons colliding with the dielectric can stimulate the emission of secondary electrons. These secondary electrons in turn accelerate toward the positive electrode. This secondary emission can lead to a runaway process where the insulator becomes positively charged and an arc forms along the surface. Accordingly, there is a need for a new pillar design that will permit the use of higher voltages without arcing.
Co-pending applications “Method For Making Field Emission Devices Having Corrugated Support Pillars for Breakdown Resistance” and “Multilayer Pillar Structure For Improved Field Emission Devices” filed concurrently herewith, disclose a corrugated dielectric pillar structure and a multilayer pillar structure, and methods for producing such pillars. These novel structures increase the surface length of the dielectric material and reduce the detrimental effect of secondary electron emission from the pillar surface. The present invention discloses a further improved pillars structure using discontinuous conductor coating with resultant improvement in resistance to breakdown and arcing of the pillars in high voltage environment.